Drawing of synthetic filaments



Oct. 11, 1966 J, Q'DONAHUE ETAL 3, 7

DRAWING OF SYNTHETIC FILAMENTS Filed Sept. 28, 1962 ATTORNEYS 3,277,641 DRAW/ENG ()F SYNTHETIC FILAMENTS James GDonahuc and Thomas Cochrane, Harrogate, England, assignnrs to Imperial Chemical Industries Limited, London, England, a corporation of Great ritain Fiied Sept. 23, 1962, Ser. No. 227,093

Claims priority, application Great Britain, Sept. 28, 1961,

2 Claims. (Cl. 57-157) The present invention relates to improvements in the drawing of synthetic filaments and to an improved drawtwisting machine used for this purpose.

In the processing of synthetic filamentary material it is usual to stretch the filaments in order to orient the molecules. In some cases it is necessary to apply heat before the stretching operation so that the operation can be carried out at high speed. One way of applying the heat is to pass the filament around a roller known as a heated feed roll which is maintained at an appropriate temperature, and then over a second roller known as a draw roll, rotating at a higher speed, the stretch occurring between the two rollers. This operation is carried out in the textile industry on machines known as drawtwisters in which a multiplicity of such rolls are driven by a common driving source.

The filaments which have been processed in this way are usually collected on a package such as a bobbin which is usually driven from the same common driving source, there being one package or bobbin for each combination of heated feed roll and draw roll. The combination of one heated feed roll, a draw roll and one packaging device forms one position on the machine, and the machines are commonly built with over 100 such positions.

In the operation of such a machine a single position can be strung up individually whilst the machine is in motion and whilst other positions are processing and packaging the filament, and similarly other positions can be broken-down individually when the package or bobbin contains the desired quantity or length of processed filament. It is desirable, however, that the multiplicity of packages produced from such a machine should each contain approximately the same quantity or length of filament so that subsequent textile operations such as warp winding are simplified. To achieve this another way of operating the machine is to string-up all the positions whilst the machine is stationary, to start the machine so that all positions, which are driven from the common driving source, start simultaneously, and to stop the machine when the desired quantity of filament has been packaged so that all positions stop simultaneously and thus the quantity of filament in each package will be approximately the sarne. As there are a multiplicity of positions, some time elapses whilst all positions are being strung-up, and during this time those filaments which were first strung-up are in contact with the heated feed roll. This time of contact with the stationary heated feed roll is much longer than would be the case where the machine strung-up whilst in motion, with the result that the filament is subjected to heat for a longer period than in the normal processing operation, and undergoes changes in its physical properties, for example a lowering of its tensile trength. When all positions of the machine have been strung-up and the machine is started, those filaments whose physical properties have been so changed are liable to break when suddenly subjected to the stretching action of the machine. Positions on which the filament has broken cannot then be used for the production of packages containing equal quantities or lengths of filament during the subsequent running time of the machine.

According to the present invention we provide, in a process for drawing synthetic filaments by means of a draw- States atent ice twister in which a multiplicity of posit-ions each comprising a heated feed roll, a draw roll and a packaging unit are driven from a common source, the improvement whereby the heated feed rolls, draw rolls and packaging units are made to rotate slowly at a crawl during the string-up operation. To enable this to be achieved our invention further provides a drawtwister wherein a conventional primary source of power such as an electric motor drives, through gearing or other form of power transmission, a number of positions each comprising a heated feed roll, a draw roll and a packaging unit, characterised by the provision of a secondary, smaller source of power connected by a free-wheel coupling to the main gearing or other form of power transmission which enables the machine to be driven at a very low speed. The smaller power source may conveniently consist of a small horse power electric motor incorporating a reduction gear in its output shaft.

The introduction of the small pony motor enables the drawtwister to be driven at speeds of the order of or 5 of its normal speed and this may be done for as long as is required for stringing-up, generally some five to ten minutes. When the stringing-up is completed the primary source of power is energised which accelerates the machine to its full operational speed, the connection to the secondary source of power being inoperative due to the action of the free wheel or over-run coupling which permits that half of the coupling normally designated the driven half to run at a faster speed than the driving half. When the drawtwister has attained its full operational speed the secondary source of power may be de-energised at will, either manually or automatically. By this technique breakage of threadlines at the start-up of the machine is minimised and there is enhanced productivity of yarn packages of constant weight.

It is to be understood that the principle of the crawlstart as set out in the foregoing description may be applied to the several types of drawtwisters commercially used for stretching synthetic thermoplastic filaments. We have found the method particularly suitable for use with drawtwisters of the heated feed roll type. We have also found the principle particularly useful when using drawtwisters which have incorporated, after the heated feed roll, a heated plate which is used to give a thermal treatment to the stretched filaments. In this case the temperature of the heated plate is usually appreciably higher than that of the heated feed roll and for this reason it is very important to minimize the time during which any particular section of filaments is allowed to dwell on the heated surfaces during the stringing-up operation.

One method of putting the process of our invention into practice is illustrated in the drawing which shows the essential parts of one position of a drawtwister comprising a heated feed roll 1, a draw roll 2, a heated plate 3 and a packaging unit 4. A secondary driving motor 5 is coupled into the main drive from the primary driving motor 6 by means of a free wheel" coupling 7 so that the feed and draw rolls 1 and 2 and the packaging unit 4 may be driven slowly while the yarn to be drawn 8 is taken from the starting package 9 and lead around the rolls over the heated plate to the packaging unit. When all positions are strung-up the primary driving motor 6 is energized and the secondary motor 5 becomes inoperative due to overrunning of the free-wheel coupling 7.

In a particular application a drawtwister of positions each comprising a heated feed roll, a draw roll, a heated plate and a packaging unit was provided with a primary power source of a 40 horse-power electric motor and a secondary driving motor of 1.5 horse-power coupled into the main gearing drive so that during the stringing-up operation the surface speed of the heated feed roll was about 5 feet/minute. This machine was used to draw polyethylene terephthalate filament yarn having a drawn denier of 50 at .an operating draw roll surface speed of 2,360 feet/minute and a packaging spindle speed of 10,250 r.p.m. It was found in repeated operation under these conditions that 90 to 95% of positions survived the acceleration from crawl to operating speeds after stringing-up at the crawl speed, that is about 110 constant weight packages were produced per machine, If attempts were made to string-up the machine while stationary and then accelerate to operating speed substantially all positions broke down.

We have found that to obtain high efficiency in terms of the number of constant weight or length packages produced from each machine it is essential to ensure that there are no loose ends of yarn present any Where in the machine to catch the freshly strung-up filaments and thus cause breakdown. We have also found that it is preferable to magnetise the traveller guide ring of the packaging unit to minimize overrunning of the traveller which may cause breakdown.

The process and apparatus of our invention may be used for synthetic filaments in general, but have been found of particular value in processing filaments of polyesters and copolyesters, e.g. those of terephthalic acid with ethylene glycol or 1,4-cyclohexane dimethanol, polyamides and polyolefines, e.g. stereoregular polypropylene.

What we claim is:

1. A method of operating a drawtwister so as to obtain appnoximately equal lengths of filaments on a multiplicity of packages, said drawtwister being of the kind having a multiplicity of positions each of which includes a heated feed roll, a draw roll and a packaging unit all driven at a high operating speed during drawtwisting by a common source, said method comprising: sequentially stringing-up at least some of said positions by stringing a filament over an associated feed and draw roll and to the respective packaging unit; driving said feed rolls, draw rolls and packaging units at a slow speed of to 5 of said high operating speed during the stringingup operation to thereby reduce the heating of a strung-up filament by its respective feed roll while subsequent positions are being strung up and to thereby reduce the tendency of the first-strung filaments to break at startup of a drawtwisting operation; thereafter simultaneously accelerating all said feed rolls, draw rolls and packaging units to said high operating speed thereby stretching and twisting said filaments; and then stopping all said feed rolls, draw rolls and packaging units at substantially the same time whereby each package contains approximately the same length of filament as a result of each filament having been wound on its respective package unit for approximately the same length of time as each other filament.

2. In a method of drawtwisting a multiplicity of filaments by stretching each filament between a separate heated feed roll and an associated draw roll operated at a higher peripheral speed and twisting and collecting the stretched filament on an associated rotating package while rotating said rolls and packages at the same high speed during a drawtwisting operation, the improvement in obtaining the same length of filament on all said packages which comprises: sequentially stringing-up at least some of the associated feed rolls, draw rolls and packaging units by stringing a filament over an associated feed and draw roll and to the associated packaging unit; rotating said feed rolls, draw rolls and packaging units at a low speed of to ,4 of said high drawtwisting speed during the stringing-up operation to thereby reduce the heating of a strung-up filament by its respective feed roll while subsequent rolls and packages are being strung-up and to thereby reduce the tendency of the first-strung filaments to break at startup of a dr-awtwisting operation; thereafter simultaneously accelerating all said feed rolls, draw rolls and packaging units to said high drawtwisting speed thereby stretching and twisting said filaments; and then stopping all said feed rolls, draw rolls and package units at substantially the same time whereby each package unit contains approximately the same length of filament as a result of each filament having been wound on its respective package unit for approximately the same length of time as each other filament.

References Cited by the Examiner UNITED STATES PATENTS 1,965,163 7/1934 Truslow 57-93 1,984,810 12/1934 Robertson 2828 2,336,100 12/1943 Jaque 5755.5 X 2,956,330 10/ 1960 Pitzl.

2,988,866 6/1961 Kleekamm et al. 5755.5 3,009,308 11/1961 Bromley et a1. 5755.5 3,018,608 1/1962 Kleekamm et al 57-157 3,025,660 3/1962 Gonsalves 57157 3,166,822 1/1965 Starkie 28-1 FRANK J. COHEN, Primary Examiner.

RUSSELL C. MADER, MERVIN STEIN, Examiners. H. G. GARNER, D. E. WATKINS, Assistant Examiners. 

1. A METHOD OF OPERATING A DRAWISTER SO AS TO OBTAIN APPROXIMATELY EQUAL LENGTHS OF FILAMENTS ON A MULTIPLICITY OF PACKAGES, SAID DRAWTWISTER BEING OF THE KIND HAVING A MULTIPLICITY OF POSITIONS EACH OF WHICH INCLUDES A HEATED FEED ROLL, A DRAW ROLL AND A PACKAGING UNIT ALL DRIVEN AT A HIGH OPERATING SPEED DURING DRAWTWISTING BY A COMMON SOURCE, SAID METHOD COMPRISING: SEQUENTIALLY STRINGING-UP AT LEAST SOME OF SAID POSITIONS BY STRINGING A FILAMENT OVER AN ASSOCIATED FEED AND DRAW ROLL AND 